adjusting driveshaft, pinion angle

[gmduramax]

So long story short I lowered the rear of my truck an inch more and I cannot get my driveshaft angles correct. I shimmed the rear of my transmission up and have shims under my axle. So the driveshaft was pointing up then would get to the pinion and I have a 6* angle there. I had a slight vibration under decel at 45-60 so I figured I needed to shim up my transmission more to get the driveshaft pointing down. I did that and holy **** does it vibrate now :spit:

So as it sits the transfercase output is 2.5* down, the driveshaft is 3.5* down so 1* angle. The pinion is 2* down so 5.5* angle.

From what I thought that should be corect. Do I have too much angle at the pinion?

 

[Bdsankey]

Sub'd

 

[Chevy1925]

So long story short I lowered the rear of my truck an inch more and I cannot get my driveshaft angles correct. I shimmed the rear of my transmission up and have shims under my axle. So the driveshaft was pointing up then would get to the pinion and I have a 6* angle there. I had a slight vibration under decel at 45-60 so I figured I needed to shim up my transmission more to get the driveshaft pointing down. I did that and holy **** does it vibrate now :spit:

So as it sits the transfercase output is 2.5* down, the driveshaft is 3.5* down so 1* angle. The pinion is 2* down so 5.5* angle.

From what I thought that should be corect. Do I have too much angle at the pinion?

So the pinion side of the driveshaft is higher or lower than the transfercase output side?

 

[gmduramax]

So the pinion side of the driveshaft is higher or lower than the transfercase output side?

Lower

 

[gmduramax]

And by raising the transmission do I have to worry about the angle of the front driveshaft?

 

[Chevy1925]

And by raising the transmission do I have to worry about the angle of the front driveshaft?

doubt it changed enough to be an issue.

ok, if raising the t-case made the driveshaft point to the ground at the pinion, you need to raise the pinion angle up. ideally you want the pinion pointed up, not down but that will change driveshaft height and working angle at both ends. see if you can make the angles close to 0 at both ends. you probably wont be able to but the pinion is pointed too far down at this point so start bringing it up. id start with 3* up on the pinion from where you are now, then re-measure all your angles

 

[gmduramax]

doubt it changed enough to be an issue.

ok, if raising the t-case made the driveshaft point to the ground at the pinion, you need to raise the pinion angle up. ideally you want the pinion pointed up, not down but that will change driveshaft height and working angle at both ends. see if you can make the angles close to 0 at both ends. you probably wont be able to but the pinion is pointed too far down at this point so start bringing it up. id start with 3* up on the pinion from where you are now, then re-measure all your angles

The trans is up almost 2 inches to get it where it is now

 

[SSchmi5519]

I thought both angles relative to the driveshaft were supposed to be equal?

 

[Chevy1925]

The trans is up almost 2 inches to get it where it is now

thats ok, the way you are lifting it is actually better than if you dropped the diff 2".

I thought both angles relative to the driveshaft were supposed to be equal?

thats the easiest way to put it for a truck that has the rear diff closer to the ground than the trans/t-case. when you get to where Anthony is, the main concern becomes the working angle which is not the same and takes a little more thought input.

 

[SSchmi5519]

thats the easiest way to put it for a truck that has the rear diff closer to the ground than the trans/t-case

Oh phew ok so as long as I remain a hillbilly I'm fine :rofl:

 

[JoshH]

This is a one piece drive shaft? It sounds very much like you need to roll the pinion up. The working angles of the u-joints should be very close to the same. You will want the pinion a little lower than what would make it exactly even because under load, the pinion will rotate up some, but the difference you have is too much. The general rule that I've always been told is no more than 3 degrees difference, and like I said, you want is so that when the pinion rotates up under load, the angles are closer together. You also need to make sure you have at least half a degree working angle. If you have zero angle at the joint, you will cause excessive wear on your joints because they won't move and you will be applying all the force into one spot.

 

[juddski88]

This is a one piece drive shaft? It sounds very much like you need to roll the pinion up. The working angles of the u-joints should be very close to the same. You will want the pinion a little lower than what would make it exactly even because under load, the pinion will rotate up some, but the difference you have is too much. The general rule that I've always been told is no more than 3 degrees difference, and like I said, you want is so that when the pinion rotates up under load, the angles are closer together. You also need to make sure you have at least half a degree working angle. If you have zero angle at the joint, you will cause excessive wear on your joints because they won't move and you will be applying all the force into one spot.

:yup:

 

[gmduramax]

Good info thanks everyone

 

[gmduramax]

Stupid question but does the driveshaft have to be pointed down in relation to the transfer case? If I take out my shims it will get the pinion side about right but it’ll push the pinion up and the driveshaft will have an upward angle at the t case and downward angle at the pinion.

 

[Chevy1925]

Stupid question but does the driveshaft have to be pointed down in relation to the transfer case? If I take out my shims it will get the pinion side about right but it’ll push the pinion up and the driveshaft will have an upward angle at the t case and downward angle at the pinion.

then the pinion wont be right. This like playing with camber and caster on the front end of the truck. if you adjust only one side of the UCA, it will move both camber and caster. In your case here, the moment you move the pinion angle, you change the t-case angle. this is why i suggested the 3* shim, not yanking all 6* out. you may not be able to get these angles perfect but you will be able to get the vibs out.

 

[JoshH]

Can you get a measurement on your drive shaft from joint to joint and a measurement on the pinion from the center of the tube to the center of the joint?

 

[gmduramax]

then the pinion wont be right. This like playing with camber and caster on the front end of the truck. if you adjust only one side of the UCA, it will move both camber and caster. In your case here, the moment you move the pinion angle, you change the t-case angle. this is why i suggested the 3* shim, not yanking all 6* out. you may not be able to get these angles perfect but you will be able to get the vibs out.

So with where it is now if I take 3* out of the pinion to move it up and have less of an angle the driveshaft will change angles at the transfer case side. So do I shim the transmission up more or let the angle change?

 

[gmduramax]

Can you get a measurement on your drive shaft from joint to joint and a measurement on the pinion from the center of the tube to the center of the joint?

I can tonight when I get back from work

 

[Chevy1925]

So with where it is now if I take 3* out of the pinion to move it up and have less of an angle the driveshaft will change angles at the transfer case side. So do I shim the transmission up more or let the angle change?

just do one thing at a time. bump it up 3*, re-measure your working angles. try to get those angles close while keeping the drivshaft flat or going down hill. if it has to go a little up hill to get good angles, im not against it but it wont take much before things go wacky.

I would REALLY like to keep the drive shaft from going up hill to the pinion. that creates greater working angles, faster and you can go to far quickly.

 

[gmduramax]

just do one thing at a time. bump it up 3*, re-measure your working angles. try to get those angles close while keeping the drivshaft flat or going down hill. if it has to go a little up hill to get good angles, im not against it but it wont take much before things go wacky.

I would REALLY like to keep the drive shaft from going up hill to the pinion. that creates greater working angles, faster and you can go to far quickly.

I’ll have to draw up a picture to make sure we’re on the same page but I think I got what you’re saying.